The invention is in the field of optical transmission cables and methods for making them.
Because individual light waveguides are not designed to withstand significant tensile loads, cable designs must include other elements for bearing tensile loads. In many cases, central rod-like strength members are used for such a purpose. In other cable designs, a tube containing optical fibers is at the center of the cable, and multiple layers of strength elements are laid concentrically therearound, including metal tubes, rod-like members, and tensile yarns.
While it is necessary for cables to withstand the ordinary stresses to which they are subjected, cost minimization is also important if light waveguide technology is ever to be offered to most individual subscribers. Such cables must also have the capacity to carry multiple light waveguides, and some applications make it desirable to house the light waveguides in a plurality of buffer tubes which may be separated from each other at a mid-span location. Therefore, cables are needed which meet all these requirements.